Chemically-induced genetic damages of cells (mammalian or submammalian) in vitro are observable by allowing the cells to express their DNA damage and the progenies with locus-specific mutation to be selected and form colonies. Statistical models have been studied. The research result has been presented to the Gordon Research Conference on Genetic Toxicology and to other meetings. It will also be presented at the l981 Joint American Statistical Association Meetings, in Detroit, Michigan.